use std::convert::TryInto;
use std::convert::TryFrom;

#[derive(Debug, PartialEq)]
struct EvenNumber(i32);
impl TryFrom<i32> for EvenNumber {
    type Error = ();
    fn try_from(value: i32) -> Result<Self, Self::Error> {
        if value % 2 == 0 {
            Ok(EvenNumber(value))
        } else {
            Err(())
        }
    }
}
fn main() {
//     TryFrom
    assert_eq!(EvenNumber::try_from(8), Ok(EvenNumber(8)));
    assert_eq!(EvenNumber::try_from(5), Err(()));
//     TryInto
    let num: i32 = 10;
    let float: f64 = num.try_into().unwrap();
    assert_eq!(float, 10.0);
    let result:Result<EvenNumber, ()> = 8i32.try_into();
    assert_eq!(result, Ok(EvenNumber(8)));
    let result:Result<EvenNumber, ()> = 5i32.try_into();
    assert_eq!(result, Err(()));
}
